CN103475061A - Photovoltaic intelligent controller - Google Patents

Abstract

The invention discloses a photovoltaic intelligent controller, which relates to the application field of photovoltaic power generation. The controller adopts the 5A multi-type battery charging management integrated chip CN3722 with solar battery maximum power point tracking (MPPT) function to charge the lithium iron phosphate battery with the highest efficiency, and the push-pull boost main circuit boosts the battery voltage Transformation, the inverter part adopts the pure sine wave inverter generator digital chip EG8010 with its own dead zone control for DC-AC power conversion. The system uses fewer chips and simple circuits to realize the process of converting solar energy into electrical energy, and obtains a 220V/50Hz pure sine wave with high precision, high reliability, and low distortion and harmonics.

Description

Photovoltaic intelligent controller

technical field

The invention relates to the application field of photovoltaic power generation, in particular to a photovoltaic intelligent controller; a controller that converts solar energy into electric energy for storage, and then inverts it into 220V/50Hz alternating current.

Background technique

In recent years, people are eager to apply new technologies of energy saving and environmental protection to solve the global energy shortage and environmental pollution problems. Recently, major cities have issued documents for the sale of individual photovoltaic power generation to the State Grid. my country is a country with large solar energy resources, so the market potential is very large. However, the controllers used for photovoltaic power generation in the market are not ideal. The charging efficiency of solar panels to batteries is low, the circuit is complicated, and the inverters all output square waves or modified sine waves, which greatly restricts the application occasions. In the inverter power supply products with pure sine wave output, the output in the form of a power frequency transformer is still promoted, and the product is bulky and expensive.

Invention content

In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a photovoltaic intelligent controller with small size, high performance, high charging efficiency, pure sine wave output, high reliability and self-protection.

The present invention is realized by the following technical solutions: a photovoltaic intelligent controller; including a solar panel, a charger connected to the solar panel, a storage battery connected to the charger, and an inverter connected to the storage battery; The charger adopts the battery charging management integrated chip CN3722; the battery is connected to the three-terminal voltage regulator LM7812 and LM7805 to output DC voltage +12V and +5V respectively; the inverter includes a boost circuit and an inverter circuit; The 12V DC is boosted by the booster circuit, and then filtered and rectified to output a 320V DC stable voltage; the inverter circuit includes an EG8010 chip, an IR2100 drive circuit and a DC/AC full-bridge inverter circuit connected to the booster circuit; the EG8010 chip generates The sinusoidal pulse width modulation signal is sent to the IR2100 drive circuit, and the IR2100 drive circuit drives the DC/AC full-bridge inverter circuit for DC-AC power conversion; the OSC1 and OSC2 pins of the EG8010 chip are externally connected to a 12MHz crystal oscillator; the pin TFB of the EG8010 chip is connected to the A temperature detection feedback circuit, the pin V _FB is connected to the output voltage feedback circuit, and the pin I _FB outputs the current feedback circuit.

The beneficial effects of the invention are: the controller realizes charging the storage battery at the maximum power point through the battery charging management integrated chip CN3722, and performs input low voltage latching, temperature monitoring, overvoltage protection and charging state indication for the storage battery. The inverter part realizes displaying the voltage, frequency, temperature and current of the inverter with the serial port LCD screen, and at the same time protects the inverter output from overvoltage, undervoltage, overcurrent and overheating. This design uses fewer chips and simple circuits to realize the process of converting solar energy into electrical energy, and obtains a 220V/50Hz pure sine wave with high precision, high reliability, and low distortion and harmonics.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 system block diagram;

Figure 2 is the charger circuit diagram

Figure 3 is a TL494 push-pull boost circuit diagram

Figure 4 is the peripheral circuit diagram of TL494;

Figure 5 is the peripheral circuit diagram of the EG8010 chip;

Figure 6 is the IR2100 drive circuit diagram;

Figure 7 is a DC/AC full-bridge inverter circuit diagram;

Figure 8 is an output voltage feedback circuit diagram;

Figure 9 is a temperature detection circuit diagram.

Detailed ways

 As shown in Figure 1, a kind of photovoltaic intelligent controller has a solar panel, the charger connected with the solar panel, the storage battery connected with the charger and the inverter connected with the storage battery; Management integrated chip CN3722; the battery is connected to the three-terminal voltage regulator LM7812 and LM7805 to output DC voltage +12V and +5V respectively; the inverter includes a boost circuit and an inverter circuit; the 12V DC of the battery is boosted The circuit boosts the voltage, then filters and rectifies it to output a 320V DC stable voltage; the inverter circuit includes an EG8010 chip, an IR2100 drive circuit, and a DC/AC full-bridge inverter circuit connected to the boost circuit; the EG8010 chip generates a sinusoidal pulse width modulation signal For the IR2100 drive circuit, the IR2100 drive circuit drives the DC/AC full-bridge inverter circuit for DC-AC power conversion; the EG8010 chip is connected to a serial port 12832 liquid crystal display module; the OSC1 and OSC2 pins of the EG8010 chip are connected to a 12MHz crystal oscillator; the EG8010 chip The pin TFB is connected to the temperature detection feedback circuit, the pin V _FB is connected to the output voltage feedback circuit, and the pin I _FB outputs the current feedback circuit.

The photovoltaic intelligent controller includes a charging circuit and an inverter circuit.

Charging part: In the independent photovoltaic power generation system, it is hoped that the excess output energy of the solar cell can be stored when the light is strong, so as to ensure that the system can also be used normally when the light is weak. The energy storage device used in this photovoltaic power generation system is a lithium iron phosphate battery with a capacity of 12V/50AH. Because it has the advantages of large capacity, light weight and volume, long life, good discharge characteristics, and environmental protection. Considering comprehensively, the performance and price are more than 4 times better than the lead-acid batteries currently commonly used. This controller adopts constant current and constant voltage charging method, the advantage of this charging method is the combination of constant current charging and constant voltage charging. Start to use constant current charging to avoid the disadvantage that the charging current is too large at the beginning of constant voltage charging, which may easily cause damage to the battery. Then, constant voltage charging is used to avoid the overcharging phenomenon caused by constant current charging and the shortcoming that the utilization rate of charging current decreases rapidly.

The charging circuit diagram composed of the battery charging management integrated chip CN3722 is shown in Figure 2. When the VCC pin voltage meets the following three conditions at the same time: (1) greater than the low-voltage latch threshold; (2) greater than the battery voltage; (3) not less than the set maximum power point voltage. The charger is working normally. The voltage of the battery terminal is fed back to the FB pin through the resistor divider network composed of resistors R6 and R7, and the CN3722 determines the charging state according to the voltage of the FB pin. If the battery voltage is lower than 66.7% of the set constant-voltage charging voltage, the charger will automatically enter the trickle charging mode, and the charging current is 15% of the set constant-current charging current. When the battery voltage is greater than 66.7% of the set constant voltage charging voltage, the charger enters the constant current charging mode, and the constant current charging current is connected to the CSP (charging current detection positive input) pin and BAT (charging current detection negative input end) set the current sense resistor RCS between the pins. When the battery voltage continues to rise close to the constant-voltage charging voltage, the charger enters the constant-voltage charging mode, and the charging current gradually decreases. When the charging current decreases to 9.5% of the set constant-current charging current, it enters the charging end state. The charging current is zero.

The battery charging management integrated chip CN3722 uses the constant voltage method to track the maximum power point of the solar battery. The so-called "Maximum Power Point Tracking" (MPPT for short) is to detect the power generation voltage of the solar panel in real time and track the highest voltage and current value (VI), so that the system charges the battery with maximum power output. The maximum power point voltage is divided by two resistors R8 and R3 and sent to the MPPT pin. In the maximum power point tracking state, the MPPT pin voltage is modulated at 1.04V, and the MPPT pin modulation voltage has a temperature of -0.4% ℃ coefficient, which is in good agreement with the temperature coefficient of the maximum power point voltage of a solar cell. The low-voltage latch circuit inside the chip monitors the input voltage. When the input voltage is lower than 6V (typical value), the internal circuit is turned off and the charger does not work.

When the input voltage loses power, the battery charging management integrated chip CN3722 automatically enters the sleep mode, and the internal circuit is turned off, which can reduce the current consumption of the battery and prolong the standby time.

In order to monitor the battery temperature, a 10kΩ negative temperature coefficient thermistor R2 needs to be connected between the TEMP pin and the GND pin. If the battery temperature is outside the normal range, the charging process will be suspended until the battery temperature returns to the normal temperature range. There is also an overvoltage comparator inside the battery charging management integrated chip CN3722. When the BAT pin voltage rises due to load changes or sudden removal of the battery, if the BAT pin voltage rises to 1.08 times the constant voltage charging voltage, The over-voltage comparator operates to turn off the off-chip P-channel MOS field effect transistor, and the charger is temporarily stopped until the voltage of the BAT pin returns to below the constant voltage charging voltage.

(充电状态指示管脚)和

(充电结束指示管脚)。COM1、COM2、COM3为回路补偿输入端。 The battery charging management integrated chip CN3722 has two status indication pins, namely

(charging status indication pin) and

(charging end indication pin). COM1, COM2, and COM3 are the input ends of the loop compensation.

As shown in Figure 3, the boost circuit adopts TL494 push-pull boost power composed of fixed frequency pulse width modulation circuit TL494, transistors Q1, Q2, field effect transistors Q3, Q4, transformer T1 and full-bridge rectifier filter circuit; The bases of Q1 and Q2 are respectively connected to the emitters E2 (pin 10) and E1 (pin 9) of the two built-in transistors of the fixed frequency pulse width modulation circuit TL494, and the emitters of transistors Q1 and Q2 are connected to the corresponding field effect transistor Q3 , the g pole of Q4, the collectors of transistors Q1 and Q2 are grounded, the s poles of field effect transistors Q3 and Q4 are grounded; the d poles of field effect transistors Q3 and Q4 are connected to the primary end of transformer T1, and the secondary terminal of transformer T1 is connected to Full bridge rectifier filter circuit.

Transformer T1 realizes the voltage change from 12V pulse voltage to 320V pulse voltage. This pulse voltage becomes 320V high-voltage DC voltage through a rectification and filtering circuit. The working frequency of transformer T1 is selected as about 50KHz. When the circuit is normal, the two built-in transistors of TL494 are turned on alternately, causing the bases of transistors Q1 and Q2 in the figure to be turned on alternately, and the field effect transistors Q3 and Q4 are also turned on alternately, so that the transformer T1 works in push-pull state, the field effect transistors Q3 and Q4 are turned on alternately at a frequency of 50KHz, so that the primary input terminal of the transformer has an alternating current of 50KHz. The polarity capacitor C3 filters out the AC component in the 12V DC to reduce input interference. Filter capacitor C1 can be taken as 2200uF. The rectification filter circuit consists of four rectifier diodes and a filter capacitor. Four rectifier diodes D3-D6 are connected in the form of a bridge, which is called a single-phase bridge rectifier circuit. In the bridge rectifier circuit, the capacitor C4 filters out the AC component in the circuit, and the filtering value here is 10uF.

The peripheral circuit of the 50HZ pulse generation chip TL494 is shown in Figure 4. Pin 15 is the inverting input terminal of the chip TL494, and pin 16 is the non-inverting input terminal. Under normal circuit conditions, the voltage of pin 15 should be slightly higher than that of pin 16 to ensure the error comparator. Only when the output is low level can the two transistors in the chip work normally. Because the chip has a built-in 5V reference voltage source, the load capacity is 10mA. So the voltage of pin 15 should be higher than 5V. The R4 of overheating protection is 200Ω, then the voltage of pin 15 is 6.22V which is greater than the voltage of pin 16. Pin 14 outputs the reference voltage, because the push-pull circuit is a double-ended output, so the output control pins 13 and 14 are connected together. Pin 12 is the power supply terminal, which is connected to an external 12V voltage. 8. Pin 11 is the collector of the final stage transistor, which is also connected to an external power supply. Pins 9 and 10 are used to output 50K pulse control switches. Pin 7 is the ground terminal, and pins 5 and 6 are externally connected with oscillating resistors and capacitors to control the output pulse frequency. Pin 4 is the dead zone control terminal. When 0-3.3V voltage is applied to it, the cut-off time can be linearly changed from 2% to 100%. This design is used to realize input overvoltage protection and undervoltage protection.

The inverter circuit consists of four parts: the inverter drive part, the DC/AC conversion part, the feedback part, and the liquid crystal display part.

1. Inverter drive circuit: The drive circuit of the single-phase pure sine wave inverter uses the single-phase pure sine wave inverter dedicated chip EG8010 as the control chip, and the drive chip uses IR2110. The OSC1 and OSC2 pins of EG8010 are externally connected with 12MHz crystal oscillator, which can realize 50Hz or 60Hz pure sine wave with high precision, little distortion and harmonics. The chip integrates SPWM sine generator, dead time control circuit, amplitude factor multiplier, soft start circuit, protection circuit, LED alarm display function, fan control function, RS232 serial communication interface and 12832 serial LCD driver module and other functions .

As shown in Figure 5, the pin PWMTYP of the EG8010 chip is used to set the PWM output type. When PWMTYP is "0", the positive polarity PWM type output is applied to the occasion where the dead zone level is simultaneously low. The EG8010 chip pins SPWMOUT1, SPWMOUT2, SPWMOUT3, and SPWMOUT4 respectively generate four groups of SPWM to drive 2 pieces of IR2110, which are respectively connected to their HIN (logic high-end input) and LIN (logic low-end input) pins, as shown in Figure 6. Among them, the pin LO and the pin HO alternately output high and low levels, and drive the four field effect transistors V1, V2, V3, and V4 to turn on alternately after passing through the resistor. The IR2110 drives the full bridge circuit as shown in Figure 6. In Fig. 6, C2 and D2 are the bootstrap capacitor and the bootstrap diode respectively, and C6 is the filter capacitor of VCC. Assume that during the period when the HO pin outputs a low level, C2 has been charged to a sufficient voltage VC1≈VCC. When HIN is high level: C2 discharges, and then C2 is equivalent to a voltage source, so that V1 is turned on. Since LIN and HIN are a pair of complementary input signals, LIN is at low level at this time, and the charges accumulated on the gate and source of V3 are quickly discharged to the ground inside the chip, and V3 is turned on at V1 due to the influence of dead time. before shutting down quickly. When HIN is low level: At this time, the charges accumulated in the gate and source of V1 are rapidly discharged inside the chip to turn off V1. After a short dead time, LIN is high level, so that V2 is turned on. At the same time, VCC quickly replenishes energy for C2 through the bootstrap diode, and the cycle repeats.

2. DC/AC full-bridge inverter circuit: adopt the full-bridge inverter mode, as shown in Figure 7, the power switch tube (IRF840) V1, V3 and V2, V4 are out of phase, and the phase difference between V1 and V2 is 180°. The output pulse width of V1 and V2, the effective value of the output AC voltage will change accordingly. AC is generated from DC to output a sine wave, and an AC voltage of 220V/50Hz is generated. Since this circuit has the function of making V3 and V4 conduct together, it has a freewheeling circuit, and even for inductive loads, the output voltage waveform will not be distorted.

3. Feedback circuit

(1) The output voltage feedback circuit is shown in Figure 5 and Figure 8. The voltage feedback processing of the EG8010 chip is to measure the AC voltage output by the inverter through the pin V _FB . The voltage sampling feedback circuit needs to be connected to the SPWM modulation bridge arm inductance At the output terminal, the circuit structure is shown in Figure 7. Calculate the error between the measured feedback peak voltage and the internal reference sine wave peak voltage of 3V, and make corresponding adjustments to the output voltage value. When the output voltage increases, the pin voltage also increases. , after calculating the error value of the internal circuit, adjust the multiplier coefficient of the amplitude factor to realize the reduction of the output voltage to achieve the voltage stabilization process; on the contrary, when the voltage of the pin is reduced, the chip will increase the output voltage.

(2) The output current feedback current is shown in Figure 5. The 220V AC output current is fed back to the I _FB pin of the EG8010 through a 100K resistor. The internal reference peak voltage of this pin is 0.5V, and the delay time for overcurrent detection 600ms, when the load current exceeds the load current of the inverter for some reason, EG8010 will output SPWMOUT1~SPWMOUT4 to "0" or "1" level according to the setting state of the pin PWMTYP, and turn off all power MOSFETs, so that When the output voltage reaches a low level, it mainly protects the power MOSFET and the load. Once it enters the over-current protection, the EG8010 will release and turn on the power MOSFET after 16 seconds to judge the load over-current situation. The duration of releasing and turning on the power MOS is 100ms. The over-current event will be judged within 100ms of the release time. If the over-current event still exists, the EG8010 will turn off all power MOSFETs to make the output voltage to a low level, and wait for the release for 16S. If the normal operation reaches more than 1 minute after the release, the EG8010 will Clear the number of overcurrent events, otherwise the EG8010 will completely shut down the output of the SPWM module if there is still abnormal operation after 5 consecutive release times, and it needs to be released after the system is powered on again.

(3) The temperature detection feedback circuit is shown in Figure 5 and Figure 9. The pin TFB of the EG8010 chip measures the working temperature of the inverter and is used for over-temperature protection detection. The NTC thermistor RT1 and the measuring resistor RF1 form a simple voltage divider circuit. The voltage divider value changes with the change of the temperature value. The magnitude of this voltage will reflect the size of the NTC resistance to obtain the corresponding temperature value. NTC uses a thermistor with a resistance value of 10K corresponding to 25°C (B constant value is 3380), and the over-temperature voltage of the TFB pin is set at 4.3V. When over-temperature protection occurs, the EG8010 will output PWMOUT1～SPWMOUT4 to "0" or "1" level, turn off all power MOSFETs to make the output voltage to low level, once enters the over-temperature protection, EG8010 will re-judge the working temperature, if the voltage of TFB pin is lower than 4.0V , EG8010 will exit the over-temperature protection, and the inverter will work normally.

4. The liquid crystal display circuit is shown in Figure 5. EG8010 supports a three-wire serial interface 12832 liquid crystal display module. This function realizes displaying information such as voltage, frequency, temperature and current of the inverter for users to observe. EG8010 pin LCDCLK is the serial port 12832 liquid crystal display module clock output terminal, LCDDI is the serial port 12832 liquid crystal display module command and data output port, LCDEN is the serial port 12832 liquid crystal display module enable terminal output.

5. Dead time setting, as shown in Figure 5, the EG8010 chip has four dead times of 300nS, 500nS, 1uS and 1.5us. The pins DT1 and DT0 of the EG8010 chip are used to control the dead time, and 4 kinds of dead time can be set, "00" is 300nS dead time, "01" is 500nS dead time, "10" is 1uS dead time, " 11" is 1.5us dead time. The dead time control is one of the important parameters of the power MOS tube. If there is no dead time or it is too small, the upper and lower power MOS tubes will be turned on at the same time and the MOS tube will be burned. If the dead time is too large, the waveform will be distorted and the power tube will heat up seriously. Phenomenon.

6. Frequency setting, as shown in Figure 5, the frequency mode of EG8010 is divided into fixed frequency mode and adjustable frequency mode. In adjustable frequency mode, EG8010 only adopts unipolar modulation mode. Pin MODSEL connected to low level. The frequency mode is set by the pin FRQSEL1, FRQSEL0, the fixed frequency mode is "00" is the output frequency of 50Hz, "01" is the output frequency of 60Hz.

7. Alarm output display, as shown in Figure 5, the EG8010 pin LEDOUT is connected to an external LED as an alarm output, and outputs a low level "0" to light up the LED when a fault occurs. The LED indication status is: long light means normal; flashing 2 times, off for 2 seconds, continuous cycle represents overcurrent; flashing 3 times, off for 2 seconds, continuous cycle represents overvoltage; flashing 4 times, off for 2 seconds, continuous cycle represents undervoltage pressure.

Working process: The solar panel charges the lithium iron phosphate battery with the highest efficiency through the 5A multi-type battery charging management integrated chip CN3722 with the function of maximum power point tracking (MPPT). Monitoring, battery terminal overvoltage protection and charging status indication and other functions. The storage battery uses three-terminal voltage regulator devices LM7812 and LM7805 to output DC voltage +12V and +5V respectively, which are used by DC loads and other chips. The 12V DC power of the battery is boosted by the push-pull boost circuit composed of chip TL494, then filtered and rectified to output a 320V DC stable voltage. After the boost main circuit is converted, the inverter part uses the EG8010 chip with its own dead zone control to generate a sinusoidal pulse width modulation (SPWM) signal to the IR2100 drive circuit, and the drive voltage type single-phase bridge inverter circuit performs DC-AC power conversion. Finally, power is supplied to the load through the output filter. The EG8010 chip protects against overvoltage, undervoltage, overcurrent, and overheating, and the external serial port 12832 LCD module displays information such as voltage, frequency, temperature, and current of the inverter.

Claims (4)

1. a photovoltaic intelligent controller; Comprise solar panel, the charger be connected with solar panel, the storage battery be connected with charger and the inverter be connected with storage battery; It is characterized in that: described charger adopts battery charging management integrated chip CN3722; Described storage battery connect Three-end voltage stabilizer LM7812 and LM7805 respectively output dc voltage+12V and+5V; Described inverter comprises booster circuit and inverter circuit; The 12V direct current of storage battery through booster circuit boost, filter rectification output 320V direct-flow steady voltage then; Described inverter circuit comprises EG8010 chip, IR2100 drive circuit and the DC/AC full bridge inverter be connected with booster circuit; The EG8010 chip produces the sinusoidal pulse width modulation signal to the IR2100 drive circuit, and the IR2100 drive circuit drives the DC/AC full bridge inverter to carry out the DC-AC power conversion; External serial ports 12832 LCD MODULE of EG8010 chip; The OSC1 of EG8010 chip, the external 12MHz crystal oscillator of OSC2 pin; The pin TFB of EG8010 chip connects temperature detection feedback circuit, pin V _fBconnect the output voltage feedback circuit, pin I _fBthe output current feedback circuit.

2. photovoltaic intelligent controller according to claim 1, it is characterized in that: described booster circuit adopts fixed frequency pulse-width modulation circuit TL494, transistor Q1, Q2, and the TL494 that field effect transistor Q3, Q4, transformer T1 and full-bridge rectification filter circuit form pushes away and exempts from the formula booster circuit; The base stage of transistor Q1, Q2 meets respectively two built-in transistorized emitter E 2 of fixed frequency pulse-width modulation circuit TL494, E1, the emitter of transistor Q1, Q2 connects the g utmost point that correspondence meets field effect transistor Q3, Q4, the grounded collector of transistor Q1, Q2, the s utmost point ground connection of field effect transistor Q3, Q4; The extremely corresponding once end that meets transformer T1 of the d of field effect transistor Q3, Q4, the secondary termination full-bridge rectification filter circuit of transformer T1.

3. photovoltaic intelligent controller according to claim 1, it is characterized in that: the EG8010 chip has 300nS, 500nS, 1uS and tetra-Dead Times of 1.5us.

4. photovoltaic intelligent controller according to claim 1, is characterized in that: the external LED of EG8010 chip pin LEDOUT.

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